Air compressor and expander

ABSTRACT

The present invention relates to an air compressor and expander including: a first rotor coupled around a driving shaft; a second rotor coupled around a driven shaft so as to operate in cooperation with the first rotor; a casing adapted to form an air compression or expansion space by the rotation of the first rotor and the second rotor; first and second end covers adapted to close the both end portions of the casing in such a manner as to have the driving shaft and the driven shaft passed therethrough in the axial direction, thereby to have the first rotor or the second rotor disposed between them; a gear part disposed on any one side of the first and second end covers in such a manner as to be coupled around the driving shaft and the driven shaft for transmitting power to the driving shaft and the driven shaft; and a clearance-preventing means disposed at the opposite side to the gear part for preventing the clearance between the end covers and the rotors.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an air compressor and expander, andmore particularly, to an air compressor and expander that is capable ofpreventing the generation of clearance between end covers and rotors inan air cycle during which air is compressed and expanded, therebyimproving refrigerating effects.

2. Background of the Related Art

As the global warming and environmental problems become severe,recently, so as to replace a refrigerant like R-134a as used up to nowwith new refrigerant, many endeavors for developing alternativerefrigerant systems have been made by all the refrigeration companiesover the world, and especially, they have studied on a new system thatis environment-friendly and has a high refrigerating efficiency, withoutany replacement of the refrigerant itself.

An air cycle that is recently considered as a most effective alternativecycle is called a reverse Bryton air cycle, which uses air asrefrigerant and reversely activates Bryton air cycle first developed asa gas power cycle, thereby obtaining the refrigerating effects.

FIG. 1 is a schematic view showing the basic principle of a general aircycle, and FIG. 2 is a graph showing the relation of T-s of the generalair cycle.

As shown, an air cycle is formed wherein a compressor 1, an expander 2,and first and second heat exchangers 3 and 4 conduct their respectivecompression process (1→2), temperature-falling process (2→3), expansionprocess (3→4), and temperature-rising process (4→1).

In the compression process (1→2), air enters the compressor 1, and aftercompressed therein, it is raised at pressure and temperature.

In the temperature-falling process (2→3), the high pressure andtemperature compressed air is transmitted to outside heat source throughthe first heat exchanger 3, and the temperature of air falls underconstant pressure condition (under the condition where pressure isslightly dropped). At this time, the high temperature air transmitted tothe outside heat source can be used as a heat source for heating an airconditioning space or for producing heated water.

In the expansion process (3→4), the air that falls at the temperature isdecreased at its pressure through the expander 2 (which has a similarstructure to the compressor), and the temperature of air falls to belowzero. At this time, the heat extracted from the expander 2 is used aspower for generating electricity or returns to the compressor 1 fordecreasing the consumption power of the compressor 1.

In the temperature-rising process (4→1), the air that falls at thetemperature and pressure is passed through the second heat exchanger 4,such that the temperature of air rises, and at this time, since heat isabsorbed from the air conditioning space, it is served for refrigeration(or freezing).

The efficiency of the air cycle is greatly dependant upon theefficiencies of the compressor 1 and the expander 2. In the past days,the compressor 1 and the expander 2 have an efficiency of about 80%, sothat the whole efficiency of the system is kept low. However, recently,the isentropic efficiency of them is raised, so that the wholeefficiency of the system is increased to 80% or more.

In other words, when the efficiency of the compressor 1 is low, power ofthe compressor 1 is increased and the compressed temperature is raised(see the compression process (1→2) in FIG. 2). When the efficiency ofthe expander 2 is low, the temperature of air is not sufficiently low,such that the refrigerating performance is decreased (see the expansionprocess (3→4) in FIG. 2).

FIG. 3 is a sectional view showing a conventional air compressor andexpander, and FIG. 4 is a perspective view showing a first rotor in theconventional air compressor and expander.

Hereinafter, since the air compressor and the air expander have thesimilar parts to each other, they will be referred to as an aircompressor and expander, for the brief description of the presentinvention.

As shown, the air compressor and expander includes: a first rotor 1coupled around a driving shaft 1 a and having a spiral type protrusion 1b formed on the outer periphery thereof; a second rotor 1 coupled arounda driven shaft 2 a so as to operate in cooperation with the first rotor1 and having a spiral type groove 1 b corresponding to the spiral typeprotrusion 1 b formed on the outer periphery thereof; a casing 3 adaptedto form an air compression space by the rotation of the first and secondrotors 1 and 2 and having first and second air flow ports 3 a and 3 bformed on the both surfaces thereof in such a manner as to be disposedperpendicular to the shafts; a closing member 4 and an end cover 5adapted to close the both end portions of the casing 3; a gear part 6formed on one side of the closing member 4 in such a manner as to becoupled around the driving shaft 1 a and the driven shaft 2 a fortransmitting power from the driving shaft 1 a and the driven shaft 2 a;and a gear box 7 adapted to cover the gear part 6.

Also, the closing member 4 and the end cover 5 are shaft-coupled tobearings 8, for supporting the rotation of the driving shaft 1 a and thedriven shaft 2 a.

Further, oil seals 9 are coupled around the first rotor 1 and the secondrotor 2 sides on the closing member 4, for preventing lubricating oilused for lubricating the gear part 6 inside the gear box 7 and thebearings 8 on the closing member 4 from flowing to the inside of thecasing 3.

Further, fixing nuts 10 are coupled to the other side of the gear part 6coupled to the first rotor 1 and the second rotor 2, for fixing thefirst rotor 1 and the second rotor 2 to the driving shaft 1 a and thedriven shaft 2 a.

The conventional air compressor and expander under the aboveconfiguration is disposed and driven in the air cycle.

According to the air compressor and expander, if the driving shaft 1 ais rotated, the first rotor 1 coupled around the driving shaft 1 a isrotated. When the first rotor 1 is rotated, the second rotor 2 coupledaround the driven shaft 2 a is rotated. At this time, since the drivingshaft 1 a and the first rotor 1, are coupled on end portions thereof bymeans of the fixing nut 10 and the driven shaft 2 a and the second rotor2 are coupled on one end portions thereof by means of the fixing nut 10,they are rotated together while the shafts are driven.

Moreover, the air flowing in through the first air flow port 3 a iscompressed or expanded, while being passed through the spiral typeprotrusion 1 b of the first rotor 1 and the spiral type groove 2 b ofthe second rotor 2, and is then discharged through the second air flowport 3 b, thereby forming the air cycle.

At this time, in case of an open-air cycle where cool air is supplieddirectly to an air conditioning space, refrigerant is respired as airitself by human beings, such that the air contaminated through mixingoil with pure air cannot be used. Thus, the air compressor and expandershould be designed to make a clearance between the first rotor and thesecond rotor set to a minimum size, such that the spiral type protrusion1 b of the first rotor 1 and the spiral type groove 2 b of the secondrotor 2 do not abut with each other. If the minimal clearance is notmaintained well, the efficiencies of the compressor and the expander aredecreased, thereby making the system performance and efficiencyundesirably deteriorated.

By the way, most of oil injection type screw compressors are configuredwherein the rotors are rotated in the engagement with each other and oilis supplied for sealing and cooling the screw threads on the rotors.However, the oil injection type screw compressors can not be applied tothe open-air cycle where refrigerant is respired as air itself by humanbeings.

According to the above-mentioned air compressor and expander, the firstrotor 1 and the second rotor 2 are moved up and down by the pressurevariations inside the casing 3 during the rotation of the first rotor 1and the second rotor 2, and the gear part 6 rotating the driving shaft 1a and the driven shaft 2 a is formed of a helical gear that is capableof reducing backlash. However, a force is generated to have the firstrotor 1 and the second rotor 2 form clearances.

That is to say, the spiral type protrusion 1 b of the first rotor 1 andthe spiral type groove 2 b of the second rotor 2 interfere with eachother by the large clearance of the first rotor 1 and the second rotor 2from the gear part 6, and thus, they are abraded, such that thetemperature of air is raised to decrease refrigerating efficiencies andthe chips coming off from the rotors are collected and attached in a lowpressure space (see FIG. 4).

In more detail, in a case where the rotors are rotated to the upper sideof the drawing, the gear part 6 coupled to the shafts has a protrusion 6a adapted to abut with the inner wheels of the bearings 8, therebypreventing the first rotor 1 and the second rotor 2 from forming aclearance from the upper side of the gear part 6, but in a case wherethe rotors are rotated to the lower side of the drawing, they do nothave any structure capable of preventing forming the clearance, suchthat the protrusion 1 b of the first rotor 1 and the groove 2 b of thesecond rotor 2 abut with each other. Especially, while the first andsecond rotors 1 and 2 are rotated at a high speed, the upper and lowerbearings 8 do not serve to sufficiently support the rotation, such thatthe interference between the protrusion 1 b and the groove 2 b is muchgenerated.

Also, according to the conventional air compressor and expander, theupper bearings are formed not abutting with oil, and during the rotationof the rotors at a high speed, the heat generated from the bearings 8 isdirectly transmitted to the air inside the casing 3, thereby decreasingthe refrigerating performance.

Further, according to the air compressor and expander having the firstrotor 1 with the spiral type protrusion 1 b formed thereon and thesecond rotor 2 with the spiral type groove 2 b formed thereon,undesirably, the space occupied by the air that flows to the rotors andis compressed therein is relatively smaller than a projection space ofthe whole rotors.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made in view of theabove-mentioned problems occurring in the prior art, and it is an objectof the present invention to provide an air compressor and expander thatis capable of having a sufficient air flow quantity to flow therein byimproving the shapes of a first rotor and a second rotor and is capableof minimizing the clearance between the first and second rotors, theclearance between the rotors and a casing, and the clearance between therotors and end covers by improving the tooth shapes of the first andsecond rotors, by disposing a closing cover at both end portions of acasing for housing the first rotor and the second rotors, and bydisposing a clearance-preventing means at one side of the closing cover.

To accomplish the above object, according to the present invention,there is provided an air compressor and expander including: a firstrotor coupled around a driving shaft; a second rotor coupled around adriven shaft so as to operate in cooperation with the first rotor; acasing adapted to form an air compression or expansion space by therotation of the first rotor and the second rotor; first and second endcovers adapted to close the both end portions of the casing in such amanner as to have the driving shaft and the driven shaft passedtherethrough in the axial direction, thereby to have the first rotor orthe second rotor disposed between them; a gear part disposed on any oneside of the first and second end covers in such a manner as to becoupled around the driving shaft and the driven shaft for transmittingpower to the driving shaft and the driven shaft; and aclearance-preventing means disposed at the opposite side to the gearpart for preventing the clearance between the end covers and the rotors.

The clearance-preventing means is adapted to make the ends of the rotorsor come into close contact with the end covers, such that the firstrotor or the second rotor does not have clearance from the end covers.

The clearance-preventing means comprises T-shaped bushings, one side ofwhich is coupled to central portion of the rotors and the other side ofwhich contacts with bearings supporting the rotors, and fasteningmembers adapted to the end portions of the driving shaft and the drivenshaft thereto to support the other side of the bearings for maintaininga predetermined distance between the gear part and the end cover.

The first end cover has a rear cover formed at the outside thereof, andthe second end cover has a front cover formed at the outside thereof.

The first rotor and the second rotor are formed twisted at apredetermined twisting angle along the axial direction, and thepredetermined twisting angle of the first rotor and the second rotor iswithin a range between 90° and 270°.

The first rotor and the second rotor are coated with Teflon on thesurfaces thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be apparent from the following detailed description ofthe preferred embodiments of the invention in conjunction with theaccompanying drawings, in which:

FIG. 1 is a schematic view showing the basic principle of a general aircycle;

FIG. 2 is a graph showing the relation of T-s of the general air cycle;

FIG. 3 is a sectional view showing a conventional air compressor andexpander;

FIG. 4 is a perspective view showing a first rotor in the conventionalair compressor and expander;

FIG. 5 is a perspective view showing an air compressor and expanderaccording to a first embodiment of the present invention;

FIG. 6 is a side view showing first and second rotors of the aircompressor and expander according to the first embodiment of the presentinvention;

FIG. 7 is a sectional view showing the air compressor and expanderaccording to the first embodiment of the present invention;

FIG. 8 is a sectional view taken along the line A-A of FIG. 7;

FIG. 9 is a perspective view showing an air compressor and expanderaccording to a second embodiment of the present invention; and

FIG. 10 is a side view showing first and second rotors of the aircompressor and expander according to the second embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, an explanation of an air compressor and expander accordingto the preferred embodiments of the present invention will be given withreference to the attached drawings.

FIGS. 5 to 8 show an air compressor and expander according to a firstembodiment of the present invention;

As shown, the air compressor and expander according to the firstembodiment of the present invention includes a first rotor 10, a secondrotor 20, a casing 30, first and second end covers 40 and 50, a gearpart 60, and a clearance-preventing means 70.

The first rotor 10 is coupled around a driving shaft 11, and the secondrotor 20 is coupled around a driven shaft 21 so as to operate incooperation with the first rotor 10. In this case, the first rotor 10and the second rotor 20 have a cycloid toothed shape.

Moreover, the first rotor 10 and the second rotor 20 are formed twistedat a predetermined twisting angle along the axial direction, and thepredetermined twisting angle of the first rotor 10 and the second rotor20 is within a range between 90° and 270°. Desirably, the first rotor 10and the second rotor 20 are coated with Teflon on the surfaces thereof.

The casing 30 is adapted to form an air compression or expansion spaceby the rotation of the first rotor 10 and the second rotor 20.

The first and second end covers 40 and 50 are adapted to close the bothend portions of the casing 30 in such a manner as to have the drivingshaft 11 and the driven shaft 21 passed therethrough in the axialdirection, thereby to have the first rotor 10 or the second rotor 20disposed between them.

An oil seal O is coupled around the driving shaft 11 and the drivenshaft 21 between the first end cover 40 and the casing 30 and betweenthe second end cover 50 and the casing 30, for preventing oil fromentering the inside of the casing 30.

Further, bearings B are mounted on each of the first and second endcovers 40 and 50 in such a manner as to be coupled around the drivingshaft 11 and the driven shaft 21, for supporting the rotation of thedriving shaft 11 and the driven shaft 21, and especially, at least twoor more bearings B are mounted on the second end cover 50 side, forminimizing the vibration upon the high speed rotation of the drivingshaft 11 and the driven shaft 21.

The gear part 60 is disposed on any one side of the first and second endcovers 40 and 50 in such a manner as to be coupled around the drivingshaft 11 and the driven shaft 21 for transmitting power to the drivingshaft 11 and the driven shaft 21, and the gear part 60 is formed of ahelical gear for preventing backlash or may be formed of a highprecision spur gear.

The clearance-preventing means 70 is disposed at the opposite side tothe gear part 60 for preventing clearance between the end covers 50 andthe rotors 10 or 20. The clearance-preventing means 70 comprisesT-shaped bushings 71, one side of which is coupled to central portion ofthe rotors and the other side of which contacts with bearings supportingthe rotors, and fastening members 72 adapted to the end portions of thedriving shaft 11 and the driven shaft 21 thereto to support the otherside of the bearings for maintaining a predetermined distance betweenthe gear part 60 and the end cover 40.

The gear part 60 has a protrusion 61 formed on one side thereof, forproviding a predetermined distance from the bearings B coupled to thefirst end cover 40.

That is to say, at the state where the protrusion 61 of the gear part 60is spaced apart from the bearings B of the first end cover 40 by apredetermined distance, the gear part 60 is coupled around the drivingshaft 11 and the driven shaft 21, and at the opposite side to the gearpart 60, the first rotor 10 and the second rotor 20 are coupled insidethe casing 30 by means of the clearance-preventing means 70 having theT-shaped bushings 71, the bearings B, and the fastening members 72, suchthat even though a force is generated, the first rotor 10 and the secondrotor 20 do not have clearance.

On the other hand, the first rotor 10 and the second rotor 20 have aring-shaped bushing 73 coupled around the driving shaft 11 and thedriven shaft 21 at the sides abutting with the first end cover 40, forcompletely preventing the first rotor 10 and the second rotor 20 fromhaving the clearances from the driving shaft 11 and the driven shaft 21.

The gear part 60 has a rear cover 80 formed around the outside thereof,for closing the gear part 60, and bearings B are fixed on the rear cover80, for supporting the driving shaft 11 and the driven shaft 21.Moreover, an oil seal O is mounted around the driving shaft 11 passedthrough the rear cover 80.

The respective bearings B that support the gear part 60, the drivingshaft 11 and the driven shaft 21 by means of the rear cover 80 arelubricated by oil, and the oil does not enter the casing 30 by means ofthe oil seals O, such that only air is compressed or expanded inside thecasing 30.

Further, the second end cover 50 has a front cover 90 formed at theoutside thereof and has a through hole 51 formed for discharging orabsorbing the compressed or expanded air within the casing 30 to andfrom a second air flow hole 91 formed at the outside of the front cover90.

In other words, the second air flow hole 91 corresponding to a first airflow hole 31 formed on one surface of the casing 30 is formed in theaxial direction on the front cover 90.

In this case, if the air compressor and expander of the presentinvention is used as an air compressor, the first air flow hole 31 is anair absorption hole, and the second air flow hole 91 is an air dischargehole. To the contrary, if used as an air expander, the second air flowhole 91 is an air absorption hole, and the first air flow hole 31 is anair discharge hole.

FIGS. 9 and 10 show an air compressor and expander according to a secondembodiment of the present invention.

As shown, the air compressor and expander according to the secondembodiment of the present invention has the same parts as in the firstembodiment of the present invention, except that the first rotor 10 andthe second rotor 20 are an involute toothed shape, and therefore, adetailed explanation on them is avoided.

Now, an explanation of the operation of the air compressor and expanderaccording to the preferred embodiment of the present invention will bein detail given.

The first rotor 10 is coupled around the driving shaft 11, and thesecond rotor 20 is coupled around the driven shaft 21. After that, thefirst rotor 10 and the second rotor 20 are disposed in the casing 30.

Also, the first and second end covers 40 and 50 are disposed at the bothend portions of the casing 30. In this case, the bearings B, the oilseals O, and the ring-shaped bushings 73 are shaft-coupled at the firstend cover 40 side, and the T-shaped bushings 71, the oil seals O, andthe bearings B are shaft-coupled at the second end cover 50 side, whilebeing fixed by means of the fastening members 72 at the end portions ofthe driving shaft 11 and the driven shaft 21.

The first rotor 10 and the second rotor 20, which are coupled around thedriving shaft 11 and the driven shaft 21 and are disposed inside thecasing 30, are supported at one sides thereof by means of the bearings Bof the gear part 60 and are fixed at the other sides thereof by means ofthe clearance-preventing means 70, i.e. the T-shaped bushings 71, thebearings B and the fastening members 72, such that as the first rotor 10and the second rotor 20 do not interfere with each other, they are notabraded, thereby improving the refrigeration capability.

Also, the rear cover 80 is fixed at the first end cover 40 side, and thefront cover 90 is disposed at the second end cover 50, such that air isabsorbed and discharged through the second air flow port 91 formed onthe front cover 90 and through the first air flow port 31 formed on thecasing 30.

Referring to the air flow when the air compressor and expander of thepresent invention is used as the air compressor, air is absorbed throughthe first air flow port 31, i.e. an air absorption port, and theabsorbed air is compressed, while being passed through the absorptionspace generated between the first rotor 10 and the second rotor 20 inthe casing 30 during their rotation. Next, the compressed air isdischarged to the second air flow port 91 of the front cover 90. i.e.the discharge port, through the through hole 51 of the second end cover50.

In this process, the first rotor 10 and the second rotor 20 are fixedaround the driving shaft 11 and the driven shaft 21, so as not togenerate a clearance from the driving shaft 11 and the driven shaft 21,thereby generating no force.

Referring to the air flow when the air compressor and expander of thepresent invention is used as the air expander, air is absorbed throughthe second air flow port 91 of the front cover 90 of the second endcover 50, i.e. an air absorption port, and the absorbed air is expanded,while being passed through the absorption space generated between thefirst rotor 10 and the second rotor 20 in the casing 30 during theirrotation. Next, the expanded air is discharged to the first air flowport 31 of the casing 30, i.e. the discharge port.

As described above, there is provided an air compressor and expanderaccording to the present invention that is provided with the first andsecond end covers disposed at the both end portions of the casinghousing the first rotor and the second rotor therein and with theclearance-preventing means disposed at any one side of the first andsecond end covers, thereby preventing the clearance between the endcovers and the rotors.

Additionally, the air compressor and expander of the present inventionhas a pair of air flow ports disposed in a perpendicular relation toeach other, thereby minimizing the pressure drop of air.

While the present invention has been described with reference to theparticular illustrative embodiments, it is not to be restricted by theembodiments but only by the appended claims. It is to be appreciatedthat those skilled in the art can change or modify the embodimentswithout departing from the scope and spirit of the present invention.

1-7. (canceled)
 8. An air compressor and expander comprising: a firstrotor coupled around a driving shaft; a second rotor coupled around adriven shaft so as to operate in cooperation with the first rotor; acasing adapted to form an air compression or expansion space by therotation of the first rotor and the second rotor; first and second endcovers adapted to close the both end portions of the casing in such amanner as to have the driving shaft and the driven shaft passedtherethrough in the axial direction, thereby to have the first rotor orthe second rotor disposed between them; a gear part disposed on any oneside of the first and second end covers in such a manner as to becoupled around the driving shaft and the driven shaft for transmittingpower to the driving shaft and the driven shaft; and aclearance-preventing means disposed at the opposite side to the gearpart for preventing clearance between the end covers and the rotors. 9.The air compressor and expander according to claim 8, wherein theclearance-preventing means is adapted to make the ends of the rotorscome into close contact with the end covers, such that the first rotoror the second rotor does not have clearance from the end covers.
 10. Theair compressor and expander according to claim 8, wherein theclearance-preventing means comprises T-shaped bushings, one side ofwhich is coupled to central portion of the rotors and the other side ofwhich contacts with bearings supporting the rotors, and fasteningmembers adapted to the end portions of the driving shaft and the drivenshaft thereto to support the other side of the bearings for maintaininga predetermined distance between the gear part and the end cover. 11.The air compressor and expander according to claim 8, wherein the firstend cover has a rear cover formed at the outside thereof, and the secondend cover has a front cover formed at the outside thereof.
 12. The aircompressor and expander according to claim 8, wherein the first rotorand the second rotor are formed twisted at a predetermined twistingangle along the axial direction, and the predetermined twisting angle ofthe first rotor and the second rotor is within a range between 90° and270°.
 13. The air compressor and expander according to claim 9, whereinthe first rotor and the second rotor are formed twisted at apredetermined twisting angle along the axial direction, and thepredetermined twisting angle of the first rotor and the second rotor iswithin a range between 90° and 270°.
 14. The air compressor and expanderaccording to claim 8, wherein the first rotor and the second rotor arecoated with Teflon on the surfaces thereof.